Five children have each been given a new ear made from their own cells in a world first. The technique is similar to the one used in the 1990s to create the famous 鈥淰acanti mouse鈥�, which had a human-like ear growing on its back.
鈥淚t鈥檚 a very exciting approach,鈥� says 听at Massachusetts Eye and Ear Infirmary in Boston. 鈥淭hey鈥檝e shown that it is possible to get close to restoring the ear structure.鈥�
The children were all born with an underdeveloped ear, a condition called microtia. This can cause hearing difficulties, says Hadlock. 鈥淐hildren with the condition often feel self-conscious and are picked on, and are unable to wear glasses.鈥�
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Standard treatments involve implanting a synthetic ear or ear-shaped cartilage taken from the child鈥檚 ribs. Neither approach is ideal: synthetic ears are prone to difficult-to-treat infections and carving rib cartilage into an ear shape is something of an art form, relying on a highly skilled surgeon.
So at Jiao Tong University in Shanghai, China, and colleagues tried something different. Their idea was to create a degradable structure based on each child鈥檚 healthy ear and populate it with the child鈥檚 own cells.
Expand and multiply
Their first attempt was carried out two and a half years ago in a girl who was 6 at the time. The team started by taking a CT scan of the healthy ear, and used this to create a 3D-printed mirror-image replica in resin. This was used to create a mould, which was filled with porous materials known to degrade in the body. The 3D-printed structure and the mould were then discarded.
The team then removed a small tissue sample from the child鈥檚 underdeveloped ear, which contained cells that make and maintain ear cartilage. At the same time, a 鈥渢issue expander鈥� was inserted under the skin of the underdeveloped ear. These devices can be injected with saline every couple of days to slowly expand and stretch the skin on top of them.
The cells from the tissue sample were multiplied in a dish until there were enough to fill the porous material of the new ear. They were then injected into the ear structure and left to perfuse into the material for 12 weeks.
Over this time they started to produce cartilage. This took over the structure as the original material degraded.
By that time, the tissue expanders had created a flap of skin the same size as the child鈥檚 healthy ear. The team then performed another operation to implant the new ear structure in the skin flap, in place of the tissue expanders.
Once implanted, the cartilage continues to grow as the degradable material disappears. It is not clear how long it takes for all the original material to be replaced, or if indeed it is ever fully replaced.
Two and a half years on, and the girl seems to be doing well. The shape, size and angle of the new ear match that of her existing healthy ear, the team says. It will continue to monitor her for another two and a half years.
Mixed results
The results of the other four procedures, which were largely the same as the first, are mixed. While all the ears have remained intact in the months since they were implanted, some have slightly distorted in shape since surgery.
For the technique to make it into the clinic, the ears will have to look better than those that are already created using synthetic materials and rib cartilage, says Hadlock. The pilot results haven鈥檛 quite reached that benchmark, she says.
鈥淭here is some change between the one-year and two-and-a-half-year mark,鈥� says Hadlock, referring to the results of the first procedure. 鈥淚f it can change a little in a year and a half, parents will want to know, what will it look like in 15 years?鈥� She also cautions that the degradable materials used to create the ear are known to break down into water, sometimes years later. This has the potential to cause swelling further down the line.
Another hurdle is the team鈥檚 use of growth factors 鈥� chemicals that help cells grow in the lab. These are commonly used in experiments, but it is unclear how safe they are for human use, says at Utrecht University in the Netherlands.
But the results do bring tissue engineering for ears a step closer to clinical use, Malda says. 鈥淭hese are the steps we need to make to bring this technology to patients,鈥� he says. 鈥淚t鈥檚 quite an achievement.鈥�
Journal reference: EBioMedicine,听
